Cells
What is the function of the nucleus in an animal cell?
It controls the activities of the cell and contains genetic material (DNA).
What is the unit of electric current?
Ampere (A)
What particles make up an atom?
Protons, neutrons, and electrons.
What is meant by an exothermic reaction?
A reaction that releases energy, usually as heat, to the surroundings.
Name the type of cell division that produces identical body cells.
Mitosis.
Give two differences between prokaryotic and eukaryotic cells.
Prokaryotic cells (e.g., bacteria) do not have a nucleus; eukaryotic cells do.
Prokaryotic cells are smaller and simpler; eukaryotic cells are larger and more complex.
What is the difference between alternating current (AC) and direct current (DC)?
AC changes direction periodically, DC flows in one direction only.
What is a covalent bond?
A bond formed when two atoms share electrons.
What is activation energy?
The minimum energy needed to start a chemical reaction.
What is cytokinesis?
The division of the cytoplasm to form two separate daughter cells.
Explain how root hair cells are adapted for their function.
They have a large surface area to increase absorption of water and minerals, and a thin wall for easy diffusion.
Describe what happens to the brightness of bulbs in a series circuit if one bulb is removed.
All bulbs go out because the circuit is broken.
Describe how the electrons behave in metallic bonding.
Electrons are delocalised and free to move throughout the metal lattice.
How does increasing temperature affect collisions between particles?
It makes particles move faster, increasing the number and energy of collisions.
What is natural selection?
The process where organisms better adapted to their environment survive and reproduce.
What is active transport?
Active transport is the movement of substances against a concentration gradient, requiring energy.
How does a light-dependent resistor in your phone (LDR) behave when the light intensity increases (persons is on their phone in the sun)?
Its resistance decreases.
How does ionic bonding result in a neutral compound?
The total positive charge of the metal ions equals the total negative charge of the non-metal ions, balancing out to zero.
Describe how catalysts affect the energy changes in a reaction.
Catalysts lower the activation energy, allowing the reaction to proceed faster without being used up
Explain why evolution by natural selection can lead to antibiotic-resistant bacteria.
Resistant bacteria survive antibiotics and reproduce, passing resistance on.
Explain why plant cells don’t burst when placed in pure water.
The cell wall provides structural support and stops the cell from bursting. The cell becomes turgid instead.
Explain why metals conduct electricity but plastics do not.
Metals have free electrons that can move and carry charge; plastics have no free electrons.
Explain why metals can be bent and shaped without breaking.
Because layers of atoms in metals can slide over each other without breaking the metallic bonds.
How does an energy profile diagram differ between exothermic and endothermic reactions?
Exothermic: products have lower energy than reactants.
Endothermic: products have higher energy than reactants.
How does meiosis lead to genetic variation?
Through independent assortment and crossing over of chromosomes.